The decalcomania printing originated from the 18th century. In the 1950's, the term “decal” roughly means water transfer printing. In the 1960's, the thermal release transfer printing technology was developed. In recent years, various transfer printing methods have appeared. The objects to be printed extended from planes to curved surfaces, and from paper to diversified materials such as plastics or metals, making the applications of the technology very extensive. To overcome the bottlenecks caused by the physical and transfer properties of different objects to be printed, various decalcomania printing forms are developed.
Specifically, decalcomania printing is a printing method of transferring the graphs or text on an intermediate carrier to an object to be printed by corresponding pressure. According to the sources of pressure, decalcomania printing can be classified to thermal decalcomania printing, water decalcomania printing, air decalcomania printing, silk-screen decalcomania printing, and low-temperature decalcomania printing.
Thermal decalcomania printing refers to printing graphs or text on a functional intermediate carrier such as paper or decalcomania film using thermal decalcomania ink. Afterwards, the intermediate carrier is heated to a certain temperature (normally 180˜230° C.) within a few minutes by using corresponding decalcomania equipment for transferring the graphs or text on the carrier to different materials.
In general, printers adopting the thermal decalcomania principle mainly use a thermal print head (TPH) module to heat the color ribbon and vaporize the dye thereon for transferring to the carrier such as paper or plastics. According to the heating time or temperature, continuous color grades are formed. A TPH module comprises a ceramic substrate, a printed circuit board, a sealing glue layer, an integrated circuit, and leads.
Nonetheless, because the substrate of the TPH module is a ceramic material, substrate breakage occurs while manufacturing large-size TPH modules. Consequently, the maximum size of current commercial TPH modules is only around 2 to 8 inches (referred to as small size). It is not possible to provide TPH modules with larger sizes, making one-time large-size printing not possible, either.
To solve the problem of manufacturing large-size TPH modules, multiple ceramic substrates are jointed for assembly in the industry. First, multiple ceramic substrates are attached to the printed circuit board, the sealing glue layer, the integrated circuit, and the leads. Then the ceramic substrates are attached to a heat dissipating plate of a long-size TPH module. By using this method, although the effective printing length is increased, the joint precision is poor. The joint gaps and differences in height between ceramic substrates still affect the quality of thermal decalcomania printing.
Accordingly, how to provide a large-size TPH module or one-time large-size printing without influencing the quality of thermal decalcomania printing has become the problem to be solved in this field.